pen: Report SDL_PenInputFlags in SDL_PenProximityEvent.

Fixes #16125.

include/SDL3/SDL_events.h

@@ -913,6 +913,7 @@ typedef struct SDL_PenProximityEvent
     Uint64 timestamp;   /**< In nanoseconds, populated using SDL_GetTicksNS() */
     SDL_WindowID windowID; /**< The window with pen focus, if any */
     SDL_PenID which;        /**< The pen instance id */
+    SDL_PenInputFlags pen_state;   /**< Complete pen input state at time of event */
 } SDL_PenProximityEvent;
 
 /**

src/events/SDL_pen.c

@@ -674,6 +674,7 @@ void SDL_SendPenProximity(Uint64 timestamp, SDL_PenID instance_id, SDL_Window *w
         event.pproximity.timestamp = timestamp;
         event.pproximity.windowID = window ? window->id : 0;
         event.pproximity.which = instance_id;
+        event.pproximity.pen_state = input_state;
         SDL_PushEvent(&event);
     }
 }